project: enable battery voltage checking

Enable battery voltage checking before flashing or erasing
image.

Change-Id: Ie95f3b88d20b19cea711f9cef980590ceed0ff89
diff --git a/project/msm8996.mk b/project/msm8996.mk
index a5f86f3..7240a30 100644
--- a/project/msm8996.mk
+++ b/project/msm8996.mk
@@ -102,3 +102,6 @@
 DEFINES += PLATFORM_USE_QMP_MISC=1
 #Use PON register for reboot reason
 DEFINES += USE_PON_REBOOT_REG=1
+
+#enable battery voltage check
+DEFINES += CHECK_BAT_VOLTAGE=1